This invention relates to a fluid flow diverter valve with an improved chamber arrangement.
It has previously been suggested that heat exchanger tubing may be internally cleaned by mounting brush-basket assemblies on the ends of the tubes, and then by flowing fluid first in one direction and then the other to cause the brushes to traverse the length of the tubes and then return to their original position. See the above-identified U.S. Pat. No. 3,319,710.
It has also been previously suggested as in the above U.S. Pat No. 3,973,592 to utilize a fourway diverter valve for purposes of reversing fluid flow within the tubes to cause the cleaning brushes to move in both directions within the tubes. In diverter valves of the '592 type a butterfly valve element having head members joined by a central plug is rotatable between normal and reverse flow positions. Four cage bars are circumferentially spaced and form pairs of opposed seats for sealing engagement with the two edges of the valve plug to connect various chambers within the valve housing with upstream and downstream fluid flow lines, depending on the rotary position of the valve element. Valves of this type have been considered subject to a number of disadvantages, namely complexity of the structure and fluid flow paths.
A more recently developed diverter valve has been thought to solve some of the problems of the valve of the '592 patent. The "pipe" valve of U.S. Pat. No. 4,506,703 utilizes no cage bars, but instead a tubular diverter having a central diametrical baffle. However, the construction of the '703 patent has been found to sometimes have distortion of the primary parts.
The German Vogler Patent DE 3340400 is also of some interest in that it discloses a fourway diverter valve which utilizes two concentric cylinders together with axially spaced chambers. This construction, however, is subject to binding problems upon relative rotation of the cylinders.
U.S. Pat. No. 4,543,996 discusses all the above U.S. patents in depth, the discussion being incorporated herein by reference. This '996 patent is indicated as presenting an improvement over the said '592 patent, and discloses a valve having a modified tapered plug with pipe segments mounted thereon as well as a pair of stub pipes which are welded to and extend inwardly from the housing walls for selective engagement with the pipe segment ends.
A problem has been perceived with the construction of the aforesaid U.S. Pat. No. 4,543,996. The stub pipes are intended to be welded to the inside of the valve housing walls so that they are aligned with diagonally positioned upstream and downstream fluid flow openings in the housing wall. The openings must be large enough to encompass the entire stub pipes, and as a result, the openings are often made larger than heretofore. At the same time, port-like nozzles are welded to the outside of the housing walls for connection to the fluid supply and a process device, such as a heat exchanger. These nozzles align with the wall openings also, but from the opposite side from the stub pipes. The stub pipes and nozzles are normally installed permanently at the point of valve manufacture. The outer ends of the stub pipes are adjusted to align with the now enlarged housing openings. In some field situations, this may be difficult if not impossible.
As a result, it has recently been suggested to eliminate the problems of the '996 valve by returning to a fourway diverter valve having four cage bars, together with a tapered valve element plug forming part of a rotatable diverter assembly. This suggested device has not been built but is known through a prior publication of a drawing, and is described hereinafter in more detail as "prior art". The assembly of the suggested device has a central portion formed with dual flow-through channels. The channel ends are delineated by a pair of annular transverse channel plates. Furthermore, a pair of annular transverse end plates are spaced axially outwardly from the respective channel plates. The plug has outer end portions which extend between adjacent channel and end plates, thus forming two fluid flow chambers at each end of the valve. In the return flow mode, fluid from the process device is split into two upper and two lower paths by the pairs of end chambers, before joining together for discharge through the return nozzle. Two pairs of axially spaced segmental plates are mounted to extend inwardly from the valve housing walls, with the channel plate edges sealingly engaging the arcuate surfaces of the segmental plates. Other features include sealing of the end plate edges at the housing end walls.
The known suggested device has also been found to be unduly complex, and due to the large number of facing elements which are in close proximity and which must slide past each other when changing between normal and reverse flow modes, undesirably high frictional or binding or sticking forces may occur. In addition, when the valve element is pre-set axially within the housing, the seal between abutting channel plates and segmental plates may be broken.
It is an aim of the invention to simplify the known suggested device, to reduce its cost and to make it of fewer parts and lighter in weight. It is a further aim to substantially reduce the tortuous fluid flow in the return mode, and to reduce undesirable friction by providing less slideable surfaces proximate each other. Yet another aim is to provide for axial pre-setting wherein sealing is not lost. It is an aim to accomplish all the above without losing the advantages of the known suggested device.
Generally, the various aims of the invention are accomplished by removing the fluid flow chambers at one end of the rotatable diverter assembly. The chamber removal is accompanied by removal of the end plate and tapered plug end portion thereat. The shape of the channel plates has also been changed. The aims are further accomplished by removal of the pair of segmental housing plates adjacent the removed end plate. The result is that all fluid flow in the return mode will be directed solely to one end of the valve element. The remaining central channels and opposite end chambers are dimensionally extended to replace the removed chambers so that the valve housing dimensions can be unchanged from the known suggested device. The aims are further accomplished by making the relationship between the edges of the remaining abutting channel plate and segmental plates of a thickness such that the effective seal therebetween is not lost when the diverter assembly is pre-set axially to set the clearance between the plug and cage bar seal surfaces.
In accordance with the various aspects of the invention, a fourway diverter valve includes a rotatable and axially shiftable diverter assembly disposed within a valve housing having a cylindrical wall and end walls as well as four circumferentially spaced cage bars. The diverter assembly is mounted on central stub shafts defining a longitudinal axis, and includes a pair of axially spaced transverse channel plates. One channel plate is disposed closely adjacent one housing end wall, while the other channel plate is disposed intermediate the housing end walls. In the present embodiment a third, or end, plate is transversely disposed on the said axis and spaced from the intermediate channel plate on the side remote from the end channel plate. The end plate is disposed adjacent the other housing end wall.
In the embodiment shown, a centrally disposed longitudinal tapered plug extends from end-to-end of the diverter assembly, joining the channel plates and also joining the intermediate channel plate with the end plate. The construction includes a pair of longitudinal generally flat channel walls spaced transversely outwardly from the plug and generally parallel to each other and the plug. Thus, a pair of side-by-side fluid flow channels are created intermediate the ends of the valve element.
A pair of diametrically opposed segmental plates or platforms are mounted to the cylindrical housing wall and extend radially inwardly between pairs of cage bars, with their inner edges being concave to receive the edges of the intermediate channel plate when the diverter assembly is in one of its positions.
When the diverter assembly is in its normal position, the plug is sealed against diametrically opposed cage bars, and the platforms and channel outer walls are not in full sealing relationship with the valve structure. The result is that all four quadrants formed by the cage bars form axial chambers which effectively extend from one end of the valve housing to the other. Adjacent chambers on each side of the plug communicate with each other. The fluid flow is generally straight through each side of the plug.
In the reverse position, the plug is not sealed but the platforms are sealed against the intermediate channel plate and the channel outer walls are sealed against the cage bar edges. The result is to form two opposed axially extending chambers which extend from end-to-end of the valve housing. In addition, there are formed pairs of transverse axially adjacent chambers which are sealed from each other, and which may be designated as upper and lower chambers. One of the axially adjacent chambers, such as the lower one, communicates with the axially extending chambers. One fluid flow path extends unidirectionally through the upper chamber, crossing opposing quadrants. The other fluid flow path is such that the fluid enters one axially extending chamber, all of the fluid hence flowing axially to the bottom chamber and around the cage bar edges and plug in both clockwise and counterclockwise directions and hence into the other axially extending chamber for discharge.
Means are provided to rotate the diverter assembly between normal and reverse positions and also to axially lift the assembly from engagement with the housing components during rotation to prevent frictional binding therebetween. The relative thickness of the oftentimes abutting channel plate and platform edges is such that effective sealing between the edges of the channel plate and platforms is not essentially lost in the reverse when there is an axial preset of the diverter assembly.